1. Field of the Invention
The present invention relates to a leadframe, and more particularly to a leadframe with different thicknesses.
2. Description of Related Art
A wire bonding technology is a common chip packaging technology applied to electrically connect a chip to a carrier. To satisfy requirements for low pin counts, a leadframe is frequently used as a chip carrier in the wire bonding technology. In most cases, the leadframe includes a die base for accommodating the chip and a plurality of leads disposed around the die base. Since the leadframe is often made of processing metal thin plates, the thickness of the die base and the thickness of the leads in the leadframe are the same.
However, the conventional leadframe with a relatively small thickness can barely achieve the heat dissipation efficiency required by a high power chip (e.g. a power source chip for controlling a power supply). Therefore, a leadframe including a relatively thick chip supporting plate, a relatively thin lead forming plate, and a connecting rod for connecting the chip supporting plate and the lead forming plate is provided. Note that the lead forming plate (the lead) cannot be excessively thick in order to comply with demands on design.
According to the related art, the leadframe with said specification can be made by rolling a metal thin plate. Nonetheless, compared with a single-gauge leadframe, the aforesaid leadframe increases the costs and prolongs a lead-time of the leadframe, particularly a brand new leadframe.